Possible causes, is the fuel tank higher than the engine? The fuel could flood the engine through the fuel return. Also,if the breather on the tank is stopped up,expansion could cause fuel to flow backwards to engine. A stuck injector would only compound the problem. I cant see it flooding all cylinders though. If the fuel rail (the passage the fuel runs through) is internal to block, the injectors will have several o rings on them. These types of engines are notorious for this problem.